1. Field of the Invention
The present invention relates to a method and device for determining when a layer of tacky material present on a cleaning member needs to be rejuvenated. Typically, the cleaning member removes contaminants such as paper dust and residual toner material from a fusing surface of a photocopying apparatus.
2. Description of the Prior Art
U.S. Pat. No. 4,013,400 describes a device for cleaning a fusing surface of a photocopier. The device has a cleaning member which is covered with a layer of tacky material for removing contaminants such as residual toner material and paper dust from the fusing surface. The device also has rejuvenators for applying a fresh layer of tacky material onto the cleaning member. The layer of tacky material present on the cleaning member is rejuvenated from time to time.
The amount of contaminants required to be removed from the fusing surface per copying cycle, however, may vary widely. Among other things, it is conditional on whether the kind of paper used gives off very little or a lot of paper dust. Periodic rejuvenation of the layer of tacky material has the disadvantage that the moment of rejuvenation will not occur when needed. If the moment of rejuvenation occurs too late, the fusing surface will be contaminated, resulting in deterioration of the copy quality. If the moment of rejuvenation occurs too early, the maximum permissible thickness of the tacky layer on the cleaning member will be reached too soon, thus, unnecessarily shortening the life of the cleaning member. Thus, there is a need to precisely determine the optimum moment for replenishment or rejuvenation of the tacky layer.
The problems associated with periodic rejuvenation are also present in other prior art devices. U.S. Pat. No. 4,000,963 describes a contact fuser asembly in a photocopier which contains a cleaning roll and a mechanism for applying a tacky material to the cleaning roll for rejuvenating the tacky surface of the cleaning roll. No method or apparatus is provided for determining when the tacky surface should be rejuvenated.
Other cleaning devices are known; however, they do not utilize a cleaning member with a tacky surface. For example, Japanese Patent Application No. 58-59484 describes an adhesive cleaning belt for removing toner from a photo receptor. A sensor detects when toner particles are present on the cleaning belt and, if present, moves a recovery roller into contact with the cleaning belt to remove the toner. There is no indication that the surface of the cleaning belt of the recovery roller is covered with a tacky material nor is any means provided for rejuvenating a layer of tacky material if it was present on either the cleaning belt or the recovery roller.
Similarly, U.S. Pat. No. 4,099,861 discloses a cleaning apparatus for removing particulate toner material from the photoconductive member of an electrophotographic copier using an air stream to entrain the toner particles. The toner particles are then removed from the air stream by a cyclone separator and a filter. It is very important that the entire cleaning apparatus be kept dry for the entrainment and subsequent removal of the toner particles. Additionally, a contamination sensor is provided to automatically shut down the copier when a malfunction occurs and excess toner particles are detected in the air stream downstream of the cyclone separator and filter.